Solve Quadratic Equation: $\mathcal{E}$ Experiment

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Discussion Overview

The discussion revolves around the conditions under which the quadratic equation $ax^2 + bx + c = 0$ has two distinct real roots, particularly in the context of the $\mathcal{E}$ experiment. Participants explore how the choice of coefficients $a$, $b$, and $c$ affects the nature of the roots, considering different scenarios for their selection.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Some participants propose that the event $A$, where the equation has two distinct real roots, depends critically on how the coefficients $a$, $b$, and $c$ are chosen.
  • One participant suggests that if the coefficients are integers chosen from a dice throw, the probability of event $A$ can be computed using basic probability principles.
  • Another participant argues that if the coefficients are complex numbers drawn from a uniform distribution, then event $A$ becomes a zero-probability event.
  • A later reply emphasizes that for the equation to have real roots, the coefficients must be real numbers, and questions how to approach the problem if they are complex.
  • It is noted that the equation has two distinct real roots if and only if the discriminant $b^2 - 4ac$ is greater than 0, with the probability of this condition being dependent on the distribution of $a$, $b$, and $c$.
  • One participant challenges the idea of a "uniform" distribution over the entire real numbers, suggesting that the probability distribution used must be specified.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the choice of coefficients and the nature of the probability distributions involved. There is no consensus on how to define the selection process for the coefficients or its impact on the event $A$.

Contextual Notes

The discussion highlights limitations regarding the assumptions about the coefficients' distributions and the implications for the nature of the roots, which remain unresolved.

Julio1
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The $\mathcal{E}$ experiment consists in choosing the numbers $a, b$ and $c$. Describe the event $A \,= \,$ the equation $ax^2+bx+c=0$ has two distinct real roots.
Hi !, I have this problem, I understand that the roots of the equation are $x=\dfrac{-b\pm \sqrt{b^2-4ac}}{2a},$ i.e., $x_1=\dfrac{-b+\sqrt{b^2-4ac}}{2a}$ y $x_2=\dfrac{-b-\sqrt{b^2-4ac}}{2a},$ but I don't understand that more there that do. :confused:
 
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How are the coefficients chosen? The answer is going to depend on that (for instance, if they are integers chosen from a dice throw the probability is going to be computable from basic probability, but if they are complex numbers drawn from a uniform distribution then $A$ is a zero-probability event).
 
Bacterius said:
How are the coefficients chosen? The answer is going to depend on that (for instance, if they are integers chosen from a dice throw the probability is going to be computable from basic probability, but if they are complex numbers drawn from a uniform distribution then $A$ is a zero-probability event).

Hello Bacterius, Thanks !

For that the equation $ax^2+bx+c=0$ has real roots, the coefficients $a,b$ and $c$ must be reals. In other hand, if $a,b,c\in \mathbb{C}$ the equation has complex roots, but how solve now the problem?
 
That wasn't what Bacterius meant when he asked how the coefficients are chosen. What probability distribution is used? It can't be "uniform" because there is no uniform distribution over the entire real numbers.

In any case, the equation ax^2+ bx+ c= 0 has two distinct real roots if and only if the discriminant, b^2- 4ac, is greater than 0. The probability of that depends upon the probability distribution of a, b, and c.
 

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